Meh.
This is going to end up being a MAC vs. PC.
You're assuming the PC user will defragment, and utilize maintenance applications.
Clearly his laptop is
slowing as stated by the OP. So, by making that assumption that people with "gaming" laptops will maintain their computers is not entirely correct.
Mid-level PC's will be outdated in the next year or two. Mac's are way more versatile, and cannot be slowed down by virus's.
Congratulations about you GF's netbook. I wouldn't want to play games on that.
To each their own. If you prefer PC's go with PC's. Mac's with Mac's. There's no convincing between the two.